Continuous lighting system for gaseous-discharge lamps with incandescent lights for standby



June 23, 1970 Aj'c, MCNAMARA, JR 3,517,254

CONTINUOUS LIGHTING SYSTEM FOR GASEOUS-DISCHARGE LAMPS WITH INCANDESCENTLIGHTS FOR STANDBY Filed May 14, 1968 5 Sheets-Sheet 1 AC 32 SOURCE A? LF34 SOURCE! A.

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Albert C. McNamara 11/.

IN VENTOR A T'IORNE Y5 June 23, 1970 A M NAMARA, JR 3,517,254

CONTINUOUS LIGHTING SYSTEM FOR GASEOUS-DISCHAHGE LAMPS WITH INCANDESCENTLIGHTS FOR STANDBY 3 Sheets-Sheet 2 Filed May 14, 1968 FIG. 8

FIG. 7

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FIG. 9

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Albert C.- Mc NarharqJlt INVENTOR BY AWM,

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ATTORNEYS june 23, 1970 A. c. M NAMARA, JR 3,517,254

CONTINUOUS LIGHTING SYSTEM FOR GASEOUS-DISCHARGE LAMPS WITH INCANDESCENTLIGHTS FOR STANDBY Filed May 14, 1968 3 Sheets-Sheet 5 m" 78 FIG/'5 f 7I i :1 30? I g 32 v i 1 v |-'J I Albert C. M cNamarqJr INVENTOR BY M W,

34 MI W FIG. /3 3- 0M A TTORNE Y5 United States Patent 3,517,254CONTINUOUS LIGHTING SYSTEM FOR GASEOUS- DISCHARGE LAMPS WITHINCANDESCENT LIGHTS FOR STANDBY Albert C. McNamara, Jr., Houston, Tex.,assignor to Esquire, Inc., New York, N.Y., a corporation of DelawareFiled May 14, 1968, Ser. No. 728,970 Int. Cl. H02h 3/20; H05b 39/10,41/46 US. Cl. 31591 Claims ABSTRACT OF THE DISCLOSURE This inventionpertains to an emergency lighting circuit that operates with a highpressure, gaseous-discharge lamp and associated ballast. When thegaseous-discharge lamp goes out, after once being ignited, sufiicientcurrent is supplied to an incandescent light or lights to maintainillumination to the area normally illuminated by the lamp. The devicefor providing this current may vary, but generally incorporates avoltage breakdown means that receives higher voltage from the ballastwhen there is failure of the gaseous-discharge lamp than when the arctherein is struck. A preferred embodiment also lights the incandescentlights during initial warm-up of the gaseousdischarge lamp. Theincandescent lights may also be used in a cold environment to maintainthe gaseous-discharge lamp sufliciently above an ambient temperaturelevel to make possible initial striking of the arc in the lamp whenambient temperature conditions might otherwise prevent it. Further,half-cycles of ballast output voltages are blocked by diodes andcapacitors are used to increase the applied voltage to enhancerestriking of the gaseous-discharge lamp in additional embodiments.

BACKGROUND OF THE INVENTION Field of the invention This inventionpertains to illumination devices and more particularly to emergencylighting circuits used in connection with gaseous-discharge lamps.

Description of prior art Gaseous-discharge lamps, such as mercury vaporand other metallic-additive vapor lamps, have long been employed inindustrial lighting situations because of their extremely highefficiency when compared to other sources, such as incandescent lights.

A gaseous-discharge lamp is a source of radiant energy characterized bythe emission of radiation from a stream of ionized vapor-carryingcurrent between electrodes in the lamp. In starting the lamp, arelatively large voltage is required. However, once current flows in thelamp, the lamp exhibits a negative resistance characteristic. That is,the resistance of the lamp decreases with an increase in current. Incommon use in the United States are fluorescent, mercury and neon lamps.

To more fully discuss the operation of circuits of the presentinvention, it is first necessary to understand more fully the operationof these gaseous-discharge lamps. Typical of such lamps is themercury-vapor lamp, which is used as an example for purposes ofdiscussion.

The mercury-vapor lamp contains an arc tube filled with argon gas and asmall amount of pure mercury. The are tube is usually mounted within anouter bulb of glass. The are tube itself is usually made of fusedquartz. One main electrode extends into the tube from one end and asimilar main electrode and a smaller starting electrode are at the otherend of the tube. The starting electrode is electrically connectedthrough a high resistance to the main electrode at the opposite end ofthe tube.

3,517,254 Patented June 23, 1970 The mercury lamp is connected throughits socket to the output leads of its ballast, which supplies propervoltage for starting and limits current during operation. When theballast circuit is first energized, no current flows, and full startingvoltage appears between the starting electrode and the adjacent mainelectrode. This voltage draws electrons across the relatively short gap,ionizing some of the argon gas in the tube and setting up a glowdischarge between these two electrodes. The resistor in the circuitlimits current to a few milliamperes. The ionized argon graduallydiifuses through the tube, reducing the resistance in the gap betweenmain electrodes. When resistance is low enough, an arc strikes acrossthe main electrodes. The heat from the arc vaporizes the droplets ofmercury, and they become ionized current-carriers as electrons in thearc bombard the vaporized mercury atoms. When all the mercury isvaporized, the current in the arc may reach several amperes. With thiscurrent flowing in the ballast, it no longer produces sufiicient voltageto maintain the initial glow, which is extinguished. The arc is thenmaintained across the main electrodes with its current limited by theballast.

If the arc is extinguished by a momentary power failure or deliberatedisconnection of the power supply, it cannot be restarted immediately.While the arc tube is still hot, the pressure created by thestill-vaporized mercury is too high to permit the formation of the glowdischarge at the starting electrode. A cooling period, ordinarily on theorder of about five minutes, is necessary to allow the mercury tocondense on the arc-tube Walls, lowering the pressure sufficiently forthe process to begin again.

The prospect of being without light for a period of time in the presenceof just a temporary cessation of power has meant that fluorescent lightshave been used in installations where gaseous-discharge lamps would haveotherwise been preferred.

Also, in a very cold environment, the possibility that an initial glowdischarge at the starting electrode will not be initiated is a distinctprobability. The ambient temperature where striking of an arc maynormally be considered assured for most gaseous-discharge lamps is 50 F.When the temperature is expected to be lower than this level, andparticularly where the temperature is expected to 'be appreciably lowerthan this level, the unreliable starting performance of such lamps hasmeant that gaseous-discharge lamps have not been used where they wouldhave been otherwise. Before the present invention, when ga'seous-discharge lamps are used in a low temperature situation, it has beennecessary to use expensive ballasts having higher internal losses thanballasts normally employed.

Among the objects and the advantages of the present invention is toovercome these two principal shortcomings by providing an emergencylighting circuit that will light in the event that the gaseous-dischargelamp with which it operates fails. Also, certain embodiments of thepresent invention include locating the incandescent lights of theemergency lighting circuit to raise the ambient operating temperature ofthe gaseous-discharge lamp, thereby aiding its ignition.

The various types of vapor lamps all possess a negative resistancecharacteristic, wherein the resistance within the lamp envelopedecreases with an increase in current. Without some form ofcurrent-limiting device in the electric circuit, current Would riseswiftly after the lamp started until lamp failure occurred. Thiscurrent-limiting element is external to the gaseous-discharge envelopeand, as referred to above, is called the ballasts of complex structuresusing inductive and capacitive reactances have been employed in ACcircuits and have increased efiiciencies when compared withresistive-type ballasts. Ballasts may take the form of simple chokes,transformers, autotransformers, a combination of these or otherstructures. Although ballast circuits of a complex nature have beenused, heretofore none has operated in the manner of the presentcircuits, as will be explained more fully hereinafter.

The present invention operates conjunctively not only with thegaseous-discharge lamp with which it is connected, but also with aballast, which would be required for operation of the gaseous-dischargelamp in any event. The present invention is not restricted to the typeof ballast employed and should not be characterized by itself as aballast circuit, but rather should be thought of as normally includingan emergency lighting circuit.

SUMMARY OF THE INVENTION The inventive circuit which is herein describedis connected to the gaseous-discharge lamp and to the ballast andincludes a voltage breakdown means, typically a diac or an SCR device,and an incandescent light located normally to illuminate the samegeneral area as that illuminated by the gaseous-discharge lamp. In asimplified version of the circuit, a diac and an incandescent lamp areconnected in series across the main electrodes of the gaseous-dischargelamp. When there is conduction between the main electrodes, the voltageapplied to the diac, as determined by the lamp and ballast action, willbe below the breakdown voltage for the diac. On the other hand, whenthere is a momentary interruption and re-establishment of power to thegaseous-discharge lamp, the lamp cannot ignite and the voltage acrossthe diac will build up beyond the threshold level of the diac. Thissupplies current for lighting the emergency incandescent light.

Other embodiments include a switching arrangement of operably connectingthe incandescent light to the power source so that it may be relativelyfree of operation of the ballast and alternately for operably connectingthe incandescent light to an independent emergency source. Additionalembodiments include connecting the incandescent light even during theinitial period of gaseous-discharge lamp warm-up (before the dischargelamp reaches full brilliance), as Well as after there has been afailure. Also, there is an embodiment described in which an emergencypower system for lighting the incandescent light uses essentially thesame wiring as the primary power system. And finally, there is anembodiment showing the raising of the peak applied voltage to thegaseous-discharge lamp to enhance starting, such embodiment alsoincluding an incandescent light or other resistor.

BRIEF DESCRIPTION OF THE DRAWINGS So that the manner in which theabove-recited advantages and objects of the invention, as well as otherswhich will become apparent, are attained can be understood in detail,more particular description of the invention briefly summarized abovemay be had by reference to the embodiments thereof which are illustratedin the appended drawings, which drawings form a part of thisspecification. It is to be noted, however, that the appended drawingsillustrate only typical embodiments of the invention and are thereforenot to be considered limiting of its scope, for the invention may admitto other equally effective embodiments.

FIG. 1. is an oblique view of a typical gaseous-discharge lamp fixtureincorporating a preferred embodiment of the present invention.

FIG. 2 is a schematic diagram of an embodiment of the present inventionusing a conventional transformer.

FIG. 3 is a schematic diagram of an embodiment of the present invention,similar to the one shown in FIG. 2, using an autotransformer.

FIG. 4 is a schematic diagram of another embodiment of the presentinvention.

FIG. 5 is a graphic representation of the voltage applied FIG. 9 is aschematic diagram of still another em bodiment ofthe present invention.

FIG. 10 is a schematic diagram of an additional embodiment of theinvention.

FIG. 11 is a schematic diagram of yet an additional embodiment of thepresent invention.

FIG. 12 is a schematic diagram of still an additional embodiment of thepresent invention.

FIG. 13 is a schematic diagram of another embodiment of the presentinvention operating in conjunction with an emergency power supply.

FIG. 14 is a schematic diagram of still another embodiment of thepresent invention operating in conjunction with an emergency powersupply.

FIG. 15 is a schematic diagram of a preferred embodiment of the presentinvention.

DESCRIPTION OF PREFERRED EMBODIMENTS Now referring to the drawings andfirst to FIG. I, a gaseous-discharge lamp fixture 10 is shown, such asmight be used for lighting an outdoor area, typically the entrance to abuilding or a parking lot. Fixture 10 includes a shield 12 secured to asupport post 14 by brackets 16 and 18 via bolt 20 in conventionalmanner, Located within shield 12 is a gaseous-discharge lamp22,ftypically of the mercury-vapor variety, and two incandescent bulbs24 and 26, which may be conveniently located within shield 12 on eitherside of lamp 22 in a symmetrical arrangement. Bolted to the bottom ofshield 12 is housing 28, in which the ballast and an electronic circuitin ac-,

cordance with the invention to be described herein is located.Appropriate leads or other connections connect lamp 22 and light bulbs24 and 26 to the circuit components within housing 28. Appropriate powerfrom an outside source may be brought into housing 28' through thehollow center of post 14.

FIG. 2 shows a simplified embodiment of the invention. Applied AC power,typically at a substantially constant 440 volts, 60 Hz., is connected toa ballast transformer 30. One end of the primary and one end of thesecondary may be grounded. The secondary is connected togaseous-discharge lamp 32. Connected in parallel with lamp 32 is aseries circuit combination comprising incandescent light 34 and diac 36or other similar voltage breakdown means. A diac may be convenientlycharacterized as being a two-terminal, bi-directional current conductmgsemiconductor.

A capacitor 35 in series with the secondary output coil of ballasttransformer 30 and lamp 32 may be employed to cause current limitingwith the popular lead type of ballast. Such a capacitor may also be usedin some of the other embodiments hereafter discussed, but for simplicitythe capacitor has been omitted.

FIG. 3 shows the same embodiment components as shown in FIG. 2, exceptthe ballast transformer is illus trated as an autotransformer 31 ratherthan as a conventional transformer.

Alternately to a ballast transformer, as shown in FIGV 4, a ballast 38,which may be merely an inductive choke coil, is shown connected to theapplied AC source. Although strictly speaking such a coil does not have.a primary and a secondary, for purposes herein the source connectionmay be thought of as being applied to the primary side of the coil andthe lamp as being applied to the secondary side of the coil.Gaseous-discharge lamp 32, incandescent light 34 and diac 36 areconnected as with the FIG. 2 arrangement.

The gaseous-discharge lamp 32 comprises typically three electrodes. Atone end thereof is a starting electrode and a first main electrodelocated adjacent thereto. At the other end is a second main electrodeconnected to the starting electrode by an extremely high resistance.Ballast transformer 30 and ballast 38 may both be characterized as beingcurrent-limiting ballast means which are connected to a main electrodeof lamp 32.

In operation of any of the foregoing circuits, operating voltage isapplied to the ballast, which is energized and produces a very highinitial peak voltage 40, such as shown in FIG. across the terminals oflamp 32. Assuming that the temperature conditions are right and thatsecondary voltage 40 is high enough to set up the initial glow dischargebetween the starting electrode and the adjacent main electrode withinlamp 32, followed rapidly by the striking of the are between the mainelectrodes, the output voltage from the ballast will rapidly decrease toa low voltage condition 42.

The time between the high voltage 40 level and low voltage 42 level isnormally so short that to the casual observer it appears that the glowis initiated instantaneously with the application of source voltage.Also, voltage 42 is quite low and well below the threshold or breakdownvoltage 128 for diac 36. Therefore, no current flows throughincandescent light 34 to ignite it. The voltage gradually increasesalong increasing slope 43 from low voltage 42 to a substantially stablevoltage level 44 which is less than the threshold level for the voltagebreakdown means.

Under normal operation of gaseous-discharge lamp 32, voltage from theoutput of the ballast will seek a stable voltage level 44 when themetallic additive in the gaseous-discharge lamp is fully vaporized andcurrent therethrough is at a maximum value. This is because the ballastfully compensates for the negative resistance characteristics of theglowing gaseous-discharge lamp.

Upon failure, even a momentary failure, of the applied AC source to theballast, and hence applied voltage to gaseous-discharge lamp 32, the arcin lamp 32 is extinguished. Normally a cooling period on the order ofabout five minutes is necessary before an are discharge can occur again.However, what does happen is that the output voltage from the ballastapplied to the series combination of diac and incandescent light againassumes a high level at a point which is above the voltage breakdownthreshold level for diac 36. This buildup occurs since the extinguishingof the are means that the resistance from main electrode to mainelectrode again becomes large. Current now passes through diac 36 andignites incandescent light 34.

Again, upon extinguishing of the arc in lamp 32, to the casual observerthere is an immediate ignition of light 34.

If light 34 is located generally to illuminate the same area as lamp 32,there is essentially continuous lighting of this area, even though lamp32 may be off for a period of minutes.

The diac and incandescent light do not have the negative resistancecharacteristics which are exhibited by lamp 32. Therefore, during thetime that light 34 is lit, the voltage applied thereto from the outputof the ballast remains relatively constant and is sufiiciently high toagain light lamp 32 when it has cooled sufiiciently.

Now referring to FIG. 6, the condition of the voltage applied to thegaseous-discharge lamp in one of the foregoing circuits during refiringof the lamp may be observed. When there is a momentary power failure,the stable voltage 49 (at the level 44 established in FIG. 5) isinterrupted, causing gaseous-discharge or are lamp 32 to extinguish.When the power is re-established at point 50, the voltage applied to thelamp is at maximum level 46 6 (at the level 40 in FIG. 5), but the lampis not in condition to refire. Level 46, being above the threshold level48 of diac 36, causes current conduction therethrough and a subsequentlighting of incandescent light 34. Hence, although arc lamp 32 isextinguished there is maintained a continuity of the existence of light.

At point 53, lamp 32 has cooled down sufiiciently to reach a favorableinternal pressure for the restriking of the arc across lamp 32. Diac 36,being a two-terminal bidirectional current carrying semiconductor, turnson with an applied voltage 48 above its threshold level and turns offeach half-cycle of the alterating current applied thereto. That is, solong as the applied voltage is above level 48, as the current goes fromone half-cycle to the next the current value passes through zero,turning off conduction in one direction through diac 36 and thenestablishing conduction therethrough in the opposite direction. When thevoltage across the terminals of lamp 32 drops from level 46 belowthreshold level 48 of diac 36, there is insufficient voltage toestablish this conduction through the diac. This causes series-connectedlight 34 to extinguish. At the time of are restriking, the voltageapplied to are lamp 32 reaches low point 52. Because some of the ions ofthe current-carrying additive in the arc lamp are still vaporized, whenthe arc is restruck the light radiating therefrom is brighter than underinitial conditions, providing sufficient light to the area withoutassistance from light 34.

Although in the above discussion, momentary power failure has beenassumed, a failure of arc lamp 32 will similarly cause light 34 tolight, as above.

FIG. 7 shows a circuit employing a serially connected diac andincandescent lamp circuit together with a diode 56. This diode permitsonly every other half-cycle of the voltage applied to it to operatelight 34. This means that the voltage rating of incandescent light 34may be lower than for the light used in the FIG. 2 circuit, all otherconditions being the same. Also, during the half-cycle in which 34 isoff, no current is drawn through the ballast, thereby providing anincrease in the peak voltage which is applied to gaseous-discharge lamp32 during the time that this lamp is being restarted. The peak value ofthe applied voltage to a gaseous-discharge light is significant, ratherthan the average value. Hence, the voltage requirements of the overallballast output are reduced.

Although the ballast means in FIG. 7 is illustrated as a transformer, aswith the FIG. 2 and FIG. 3 structures, this means could take the form ofa choke coil, such as coil 38 as shown in FIG. 4, or other equallysuitable structure. This possibility exists for the other embodiments tobe hereinafter described, as well.

FIG. 8 shows an embodiment of the circuit shown in FIG. 7 (illustratedto include a choke coil, rather than a transformer, merely forillustrative purposes) with the addition of capacitor 39 in parallelacross diode 56 and light 34. It may be recalled that during the periodwhile arc lamp 32 was cooling down to the conditions for restriking,between points 50 and 53 on FIG. 6, the voltage across the terminals oflamp 32 reached a level 46. Because current was passing through light 34and its series circuit during this period, this voltage level 46 appliedto lamp 32 was actually less than in the initial condition (level 40 inFIG. 5). With the addition of capacitor 39 it has been found that duringthe non-conductive halfcycles of diode 56, the peak voltage applied tolamp 32 is larger than otherwise, thereby aiding in the restrikingaction. Typically, without the capacitor, the peak voltage may be 360volts while with the capacitor, this level is increased to 625 volts.

Of course, even without the slight drop in voltage during the periodbefore restriking occurs, the capacitor would cause a larger peakvoltage on the terminals of the arc lamp than otherwise, but this isparticularly important when there is a slight voltage drop as abovedescribed since the operation of the arc lamp may be made marginal bythe voltage drop without the voltage increase.

The conductive half-cycles of diode 56 allow the current to bleed offcapacitor 39 to prevent excessive build-up thereon. Also, since diode 56has a very small threshold compared with diac 36, once arc lamp 32 hasan arc struck therein, and light 34 goes out, capacitor 39 will notmaintain a charge, again discharging through light 34.

It should be further noted that this voltage aiding quality of capacitor39 in this circuit eXiSts even when a suitable and similar-valueresistor is substituted in place of light 34, should there be norequirement for the emergency lighting benefit of light 34 in aparticular installation.

Although illustrated with respect to the FIG. 8 circuit arrangement, thecapacitor may be used similarly in the other circuits to be laterdescribed herein that have a diode similar to diode 56 or otherrectifier-type means for causing half-cycles of the arc lamp terminalvoltage to be blocked.

FIG. 9 shows yet an additional embodiment of the invention employing twosymmetrical voltage breakdown means, namely, diacs 58 and 60, in serieswith light 34. This merely reduces the voltage ratings of the diacs, butotherwise the operation is identical with the circuit shown in FIG. 2.

FIG. 10 shows an embodiment utilizing for the voltage breakdown means anSCR 62 having a suitable triggering means for gating the SCR onhalf-cycles of the operating voltage from the ballast when there iscessation of condition in the gaseous-discharge lamp 32. Operationally,this circuit is quite similar to that shown in FIG. 7. This triggeringmeans comprises, conventionally, an integrator made up of capacitor 64and resistor 66 which applies a signal through diac 68 to the gateelectrode on SCR 62. The anode and cathode of SCR 62 are connected inseries with incandescent light 34. Hence, the gate turns on the SCR whenthere has been failure of lamp 32, thereby lighting the incandescentlight 34 on alternate half-cycles. Also, peak voltages of alternatehalf-cycles are applied to gaseous-discharge lamp 32 during operation ofthe SCR so that lamp 32 has the maximum eifective operating voltageapplied thereto.

Still further embodiments of the invention are shown in FIGS. ll, 12 and13. In FIG. 11, a trigger circuit comprising a resistor 70, capacitor 72and diac 74 is shown connected in parallel with the gaseous-dischargelamp 32, as with the FIG. 10 structure. In this embodiment, however,incandescent light 34 is connected in series with the cathode and anodeof an SCR 76, the combination of which is supplied power from theprimary source, rather than from the output of the ballast.

FIG. 12 shows another embodiment which places the incandescent light 34across the input source voltage, although when light 34 comes on it iscontrolled by the voltage across the main electrodes of discharge lamp32. In this case a diac 78 is connected in series with a relay coil 80,the series combination being connected in parallel across lamp 32. Thecontacts associated with relay coil 80 are normally open when there isno conduction through diac 78. When there is conduction through the diac78 (signifying that there is cessation of conduction in lamp 32) relaycoil 80 is energized closing contacts 82, thereby applying primary powerto incandescent light 34.

FIG. 13 shows the same type of operation as FIG. 12, except that uponclosing of relay contacts 82 an auxiliary source is applied to theincandescent light, rather than the primary source which is applied tothe gaseous discharge and ballast circuit.

The FIG. 14 embodiment of the invention is similar to the FIG. 7embodiment, except that this embodiment also incorporates an auxiliaryemergency supply system which uses much of the same wiring as theprimary system uses. Connected in parallel across main supply 84 is anormally-energized relay coil 87 of control circuit 88, the relay coilhaving associated therewith normally-closed contacts 89 andnormally-open contacts 91. One connection from source 84 is tieddirectly to the ballast/arc lamp network and the other connection isconnected through normally-closed contacts 89. One connection fromemergency supply source 86 is likewise tied directly to the ballast/arclamp network. However, the other connection is connected through thenormallyopen contacts 91.

It may be seen that upon failure of the main supply 84, the emergencysupply is placed across the input of the ballast. Since there is noreturn for relay coil 87 when emergency supply 86 is supplying operatingpower to the circuit, relay coil 87 is not energized until main supply84 is re-established. The re-establishment of the main supply reversesthe switching operation from main to emergency source operation justdescribed. Of course, any similar control and switching circuit ofsimilar conventional design may be employed.

Connected to the secondary of ballast 30, as previously stated, is anarrangement of components similar to that shown in FIG. 7, although thevariations shown in FIGS. 2-4 and 7-12 may also have been used. However,when a diode 56 is used in series with light 34, the embodimentsemploying a capacitor in series between the ballast and the arc lamp,such as shown in FIGS. 2 and 3, cannot be used. The illustratedcomponents include a series combination of a diac 36, a diode 56 andincandescent light 34 connected across the output of ballast 30. Thereis a difference, however, in that normally-closed contacts 90 areincluded in series with gaseous-discharge lamp 32, this seriescombination being connected across the output of ballast 30.

Connected across the input of ballast 30, or across the output of mainsource 84, is a typical bridge rectifier 92 in series with capacitor 94.Connected to the output of rectifier 92 is relay coil 96 associated withcontacts 90 in the gaseous-discharge circuit.

Main supply source 84 is typically at line voltage of 60 Hz., which iseffectively blocked by capacitor 94. Therefore, relay coil 96 connectedto the output of rectifier 92 is not energized so long as main supply isbeing provided to the overall circuit. Normally closed re-.

lay contact 90 allow ignition of gaseous-discharge lamp 32 as before.However, when main supply fails, emergency source 86 operates thecircuit. Typically, the frequency of source 86 is 400 Hz., or afrequency much higher than source 84. Capacitor 94 is such that itallows this relatively high frequency to pass to bridge 92,. the outputof which, in turn, energizes relay coil 96. Relay coil 96 opensnormally-closed contacts 90 to prevent lamp 32 from re-igniting from theemergency source.

Therefore, when main supply 84 is somewhat permanently disconnected fromthe circuit, not just merely temporarily disconnected, incandescentlight 34 is lit by the emergency supply. When main supply 84isre-established and supply 86 is disconnected by control 88,then

contacts 90 close and allow discharge lamp 32 to again i be ignited. Iflamp 32 is still not in a suitable state for restriking, incandescentlight 34 is operated from supply 84 as described previously.

FIG. 15 shows a circuit in which the associated incandescent lights 98and 100 operate a little bit differently than the incandescent lights inthe other embodiments.

Notice that connected in series with incandescent lights 98 and 100 arerelay contacts 102, all of which are connected in series with source104. Relay contacts 102 are normally closed, so that upon application ofvoltage from source 104 lamps 98 and 100 immediately light.

Also connected to source 104 is ballast 30, as with the otherembodiments, across the output of whichis discharge lamp 32, as before.Also connected across the output of ballast 30 is a typical bridgerectifier 106. The output of the bridge rectifier is connected acrosstwo series of circuits. The first of these series circuits includesnormally closed relay contacts 108, diac 110, resistor 112,

and relay coil 114. Connected in parallel across resistor 112 and relaycoil 114 is resistor 116 for a purpose to be described hereinafter.Relay coil 114 is that relay coil which is associated with contacts 102.

The other series combination connected across the output of rectifier106 includes, in series, diac 118, resistor 120 and relay coil 122.Resistor 124 is connected in parallel across resistor 120 and relay coil122.

To consider the operation of this circuit, again refer to FIG. 5.Immediately upon initial striking of gaseousdischarge lamp 32, thevoltage output from ballast 30 is at low voltage 42. Voltage applied todiac 110 gradually increases along slope 43 until it reaches turn-onthreshold level 126 of diac 110. At this time relay coil 114 isenergized, opening relay contacts 102 and extinguishing incandescentlights 98 and 100. By the time this happens, the light from lamp 32 isbright enough to illuminate the area.

Should the gaseous-discharge lamp be extinguished because of momentarydisconnection of power thereto, the voltage applied to diac 118 willrapidly rise until its threshold level 128 is surpassed, therebyapplying energizing current to relay coil 122. When relay coil 122 isenergized, relay contacts 108 associated therewith are opened, which inturn de-energizes relay coil 114. When relay coil 114 is de-energized,normally closed relay contacts 102 associated therewith are closed,applying igniting current to lights 98 and 100 from source 104.

As with the other embodiments, following the cooling period for lamp 32,an arc restrikes. Although the voltage applied to diac 118 is quicklyreduced below the conduction turnoff level for diac 118 so that relaycontacts 108 are closed, the voltage applied to diac 110 has temporarilybeen removed so that it is necessary to build up to threshold level 126before diac 110 again conducts. Conditions at this point are as theywere initially, in that threshold level 126 has to be exceeded beforerelay coil 114 is energized, resulting in relay contacts 102 associatedtherewith being opened to turn 01f lights 98 and 100. Also, as in theinitial operating conditions, the constant level voltage under normaloperation never exceeds threshold level 128 to cause diac 118 toconduct. Of course, if there is again failure as before, diac 118 willconduct automatically reinitiating the cycle again as previouslydescribed.

Resistors 112 and 120, respectively, are provided to match relay coils114 and 122 to the voltage drop requirements of operation, if requiredby the voltage rating of the coil. For example, if the voltage from therectifier is 240 volts and relay coil is designed for 120 voltoperation, the series resistor is added to provide a 120-volt drop.Resistors 116 and 124, respectively, provide a holding current for diacs110 and 118, respectively, to prevent chatter of relay contacts 102 and108, respectively, once the respective coils are positively energized.

As has been previously mentioned, in the FIG. 1 embodiment themetallic-additive lamp is shown in the same fixture as the incandescentlights. This may be convenient to provide the necessary heating in acold environment so that the ambient temperature is conducive toconduction for the gaseous-discharge lamp once the pressure therein isright for the striking of an arc. In fact, a high resistance means thatradiant heat may be employed in place of such incandescent light if theemergency lighting feature of such light is not important in aparticular installation.

It may be desirable in many instances to locate the incandescent lightoutside of the fixture or in an entirely different location, which in noway interferes with operation of the overall lamp operation underordinary ambient temperatures, normally about 50 F.

While several embodiments of the invention have been described, it isobvious that various substitutions or modifications of structures may bemade without varying from the scope of the invention.

What is claimed is:

1. An emergency lighting system comprising:

a gaseous-discharge lamp,

means for applying a voltage to said gaseous-discharge lamp to igniteand operate said gaseous-discharge lamp,

incandescent light means, and

control voltage breakdown means having a threshold level greater thanthe normal operating voltage across said gaseous-discharge lamp and lessthan the peak starting voltage applied to said gaseous-discharge lamp,said voltage breakdown means responsive to the extinguishment of saidgaseous-discharge lamp for connecting said incandescent light means tosaid voltage applying means to provide emergency lighting, said voltagebreakdown means further responsive to the re-ignition of saidgaseous-discharge lamp for disconnecting said incandescent light meansfrom said voltage applying means.

2. An emergency lighting system as described in claim 1,

wherein said voltage breakdown means is connected in series with saidincandescent light means to form a series combination, and said seriescombination is connected in parallel with said gaseous-discharge lamp.

3. An emergency lighting system as described in claim 2,

wherein said applied voltage is an AC voltage, and

said voltage breakdown means includes an SCR having a trigger circuitfor gating the SCR on first half-cycles of the operating voltage whenthe gaseous-discharge lamp is extinguished, providing correspondinglyhigh peak second voltage half-cycles to the gaseousdischarge lamp.

4. An emergency lighting system as described in claim 2, wherein saidapplied voltage is an AC voltage, and

said voltage breakdown means is a two-terminal bidirectional currentconducting semiconductor.

5. An emergency lighting system as described in claim 4, wherein saidvoltage breakdown means includes a rectifier in series with saidtwo-terminal bi-directional current conducting semiconductor, the firsthalf-cycles of current through said conducting semiconductor ignitingsaid incandescent light means, the second halfcycles of current throughsaid conducting semiconductor being blocked and providingcorrespondingly high peak voltage half-cycles to the gaseous-dischargelamp.

6. An emergency lighting system as described in claim 4 wherein saidvoltage breakdown means includes a rectifier in series between saidtwo-terminal bi-directional current conducting semiconductor and saidincandescent light means, the first half-cycles of current therethroughigniting said incandescent light means, the second half-cycles ofcurrent therethrough being blocked and providing correspondingly highpeak voltage half-cycles to the gaseous-discharge lamp, and

a capacitor across said rectifier and said incandescent light means tofurther increase the high peak voltage half-cycles to thegaseous-discharge lamp.

7. In combination with a gaseous-discharge lamp having a first mainelectrode and a second main electrode,

current-limiting ballast means having an input and an output, saidoutput connected to at least one of said first and second mainelectrodes, and

means for applying a voltage across the input of said ballast means,

an emergency lighting system, comprising incandescent light means,

a switch connected to form a series combination with said incandescentlight means, said series combination being connected to the voltagemeans applied to the input of said ballast means, and

voltage breakdown means for closing said switch in response to theextinguishment of said gaseous-discharge lamp to light said incandescentlight means.

8. An emergency lighting system as described in claim 7, wherein saidswitch is the anode and cathode of an SCR, and

said voltage breakdown means includes a two-terminal bi-directionalcurrent conducting semiconductor and the gate electrode of said SCR.

9. In combination with a gaseous-discharge lamp having a first mainelectrode and a second main electrode, and

current-limiting ballast means connected to at least one of said firstand second main electrodes,

an emergency lighting circuit, comprising incandescent light means,

a first switch connected to form a series combination with saidincandescent light means, said series combination being connected to anoperating voltage applied to the input of the ballast means,

trigger means for controlling said first switch, including first voltagebreakdown means having a second switch and connected to the output ofthe ballast means, breakdown voltage above its threshold level beingapplied thereto while there is conduction between the first and secondmain electrodes, conduction of said first voltage breakdown meansopening said first switch, and

second voltage breakdown means connected to the output of the ballastmeans, breakdown. voltage above its threshold level being appliedthereto upon cessation of conduction between the first and second mainelectrodes, conduction of said second breakdown means opening saidsecond switch, and thereby closing said first switch to light saidincandescent light means.

10. In combination with a gaseous-discharge lamp having a first mainelectrode and a second main electrode, and

current-limiting ballast means connected to at least one of said firstand second main electrodes,

a high peak voltage restriking circuit, comprising voltage breakdownmeans,

a rectifier connected in series with said voltage breakdown means,

a resistance means connected to form a series combination with saidvoltage breakdown means and said rectifier means,

said series combination being connected in parallel across thegaseous-discharge lamp,

operating voltage applied across the ballast means and thegaseous-discharge lamp establishing a voltage across said voltagebreakdown means below its threshold level while there is conductionbetween the first and second main electrodes,

momentary interruption of operating voltage causing a period ofcessation of such conduction resulting in voltage being applied acrosssaid voltage breakdown means above its threshold level,

the first half-cycles of current through said rectifier passing throughsaid high resistance means, the second half-cycles of currenttherethrough being blocked and providing correspondingly high peakvoltage half-cycles to the gaseous-discharge lamp, and

a capacitor connected across said rectifier and said high resistancemeans to further increase the high peak voltage half-cycles to thegaseous-discharge lamp, the charge on said capacitor discharging throughsaid resistance means during first half-cycles of current through saidrectifier.

11. In combination with a gaseous discharge lamp having current limitingballast means connected thereto, in emergency lighting systemcomprising:

means for applying a voltage to the ballast means and gaseous-dischargelamp suflicient to ignite and operate said gaseous-discharge lamp,

incandescent light means, and

voltage breakdown means for connecting said incandes cent light means tosaid voltage applying means when said gaseous-discharge lamp isextinguished to light said incandescent light means, and fordisconnecting said incandescent light means from said voltage applyingmeans a predetermined time after said gaseous-.- discharge lamp isre-ignited, and upon said gaseousdischarge lamp reaching a predeterminedbrightness.

12. In combination with a gaseousdischarge lamp having a first mainelectrode and a second main electrode, and

current-limiting ballast means connected to at least one of said firstand second main electrodes, an emergency lighting system, comprisingvoltage breakdown means having a threshold level greater than the normaloperating voltage across said gaseous-discharge lamp and less than thepeak start ing voltage applied to said gaseous-discharge lamp,

incandescent light means; and

means for applying an operating voltage across the ballast means and thegaseous-discharge lamp to establish a first voltage across said voltagebreakdown means below its threshold level while there is conductionbetween the first and second main electrodes, momentary interruption ofsaid operating voltage causing a period of cessation of such conductionresulting in a second voltage being applied across said voltagebreakdown means above its threshold level, to light said incandescentlight means, said second voltage being reduced to said first voltageupon resecond voltage breakdown means connected across saidgaseous-discharge lamp having a predetermined threshold level less thanthe normal operating voltage of said gaseous-discharge lamp,

control means responsive to said first voltage breakdown meansconducting upon extinguishment of said gaseous-discharge lamp forlighting said incandes-- cent light means and for disabling said secondvoltage breakdown means, said control means further responsive to saidfirst voltage breakdown means re-,

suming its blocking state upon re-ignition of said gaseous-dischargelamp for enabling said second voltage breakdown means, said secondvoltage breakdown means conducting after the gaseous-discharge lampreaches a predetermined brightness to extinguish:

said incandescent light means. 14. An emergency lighting system as setforth in claim 13 including rectifier means having an input connectedacross the gaseous-discharge lamp and an output, and wherein said firstvoltage breakdown means and said second voltage breakdown means areconnected across the output of said rectifier means. 15. An emergencylighting system as described in claim 14 wherein said control meansincludes a first relay coil connected 1.3 14 to the output of said firstvoltage breakdown means 2,043,023 6/1936 Westendorp 315-182 X foractuating first relay contacts which are connected 2,431,151 11/ 1947Tellegen 315179 X in series with said second voltage breakdown means,2,871,409 1/ 1959 Aldrich et a1 315-406 X and a second relay coilconnected to the output of 3,204,120 8/1965 Nakem 307318 X said secondvoltage breakdown means for actuating 5 3,412,392 11/ 1968 Jenkens eta1. 317--31 X second relay contacts which are connected in series3,343,085 9/1967 Ovshinsky 31731 X with said incandescent light means.

JAMES W. LAWRENCE, Primary Examiner C. R. CAMPBELL, Assistant ExaminerReferences Cited UNITED STATES PATENTS 10 1,909,072 5/1933 Prescott315-453 1,970,519 8/1934 Dorgelo et a1. 315--192 X 307 3 )5; 315 92, 93,1 2; 317 31 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PatentNo. 3 ,517 ,254 June 23 1970 Albert C. Mo Namara Jr peers in the aboveidentified ied that error ap are hereby corrected as It is certif ettersPatent patent and that said L shown below:

line 29, "condition" should read conduction Column 7, Column 10, line 6,"control" should be deleted. Column ll, line 74, "in" should read anSigned and sealed this 2nd day of March 1971.

(SEAL) Attest:

Edward M. Fletcher, 11'. Commissioner of Patents Attesting Officer

